Provided is a compound useful as an AMPK activator. The compound is a compound represented by the formula or a pharmaceutically acceptable salt thereof. In the formula, Y represents a substituted or unsubstituted alkyl group or the like; T represents -CR7= or -N=; U represents -CR8= or -N=; R2 represents a hydrogen atom or the like; R3 represents a halogen atom or the like; and R4, R7 and R8 independently represent a hydrogen atom or the like.